Shaft restraining device



F: M. LEWIS SHAFT RESTRA'INING DEVICE March 5', 1946.

Filed July 10,- 1943 ATTOEWE Y.

Patented Mar. 5, 1946 UNITED m:

SHAFT nrzsrnammd DEVICE Frank M. Lewis, Weston, Mass. a Application July10,1943, Serial No.4945201 4Claims. (cuss-soy I I (Granted under the actof March a; 1883, as;

1 amended April 30, 1928; 370 0.

The invention relates to a device for restraining high frequency axialmovement of a shaft subject to high frequency forces, such as thepropeller shaft of a ship.

The axial thrust exerted by the screwpropeller of aship ordinarily istransmitted along the propeller shaft to the ship structure through athrust bearing at the forward end of the propellershaft.

The propeller shaft is subjected not only to a sub tantially steadyforward thrust but also to objectionable highfrequencyaxial movementswhich tend to cause vibration in the ship structure and which may causeexcessive wear or damage in the main thrust bearing. H o,

It is, therefore, the primary object of the present invention to providea propeller shaft with a device which will resist high frequency axialmovement of the shaft without appreciably interfering with thetransmission of substantially steady forward thrust therealong. Y

Another object of the invention is to. provide a propeller shaft withmeans for transferringany high frequency axial forces from the shaft tothe ship structure in a zone where such high frequency forces may bereceived with less possibility of causing damage or objectionablevibration in the ship.

A further object of the invention is the provision of a viscous damperadapted to limit the motions of the propeller-shaft-engine system markedly at resonance. r

Other objects and advantages of the invention will become apparentduring the course of the following detailed description, taken inconnection with the accompanying drawing, forming a part of thisspecification, and in which drawing,

Figure 1 is a side elevational. view of the restraining device, withportions of its supporting tructure shown in vertical section.

Figure 2 is a vertical transverse sectional view taken substantially onthe line 2-2 of Figure 1.

Figure 3 is a central vertical longitudinal sectional view of therestraining device.

On the drawing, which for the purpose of illustration, shows only apreferred embodiment of the invention, and wherein similarreferencecharacters denote corresponding parts throughout the severalviews, the numeral l designates the propeller shaft of the ship,provided with a fixed cylindrical enlargement hereinafter referred to asa piston ll, preferably integral with the propeller shaft.

Surrounding the piston II is a cylindrical housing l2 which may includeupper and lower halves I 3, l4, defining a chamber l5 and provided alongtheir meeting edges with longitudinal flanges" iii, l'l clamped togetheras by bolts 18.

A small clearance, averaging on the order of 0.004 inch for a, shipinstallation, is maintained about the piston I I. Due to strengthrequirements,

For this reason,

bearing sleeves the example shown the principal elements of the deviceare ordinarily madeofsteel. Sinceithe parts are heavy-and the clearanceabout the piston'is small, surface contact between the piston H and thelowe half of the housing l2 wouldbe practically unavoidable.

the chamber I5 is made of a dithan that of-' the piston-H, and orliners! 9, 20 that provide the desired clearance about the piston arefixed'within the housing. The sag of the pistonll due to its weight issomewhat exaggerated in Figure 3 and in light weight constructions-wouldnot'be appreciable. However, thissag-does not seriously affect theoperation of the device although it'may eliminate, except forthefthickness'of a film of oil, the clearance between'the' piston I Iand the lower half I401 the housing.

These liners I 51:20, are tapered in thickness outwardly from aboutmidway oi their widths, as indicated at 2 I, soas to take care ofpossible axial misalignment ofthe propeller shaft l0 and the housing l2.In order'to facilitate assembly, the

ameter greater liners'are split, as indicated at22.

The opposite ends of the housing l2 are sealed about the shaft in anyconvenient manner. In in- Figure 3, the housing'ends are'each providedwithstufilng boxes 23 equipped with glands 24. adjustable as For ease ofassembly on shipboard, the glands 24 are of' the split ty removablysecured together, asby cap screwszaf tion tothe shaftollljandfinwardlyof the stuffing boxes 23 are sealing rings 21., .In theexample shown in Figure 3, each endof the'housi'ng I2 is providedv withthree. number of rings maybeused. p 7 l ,In order that oil underpressure may beclrculated through the housing l2, oil su ply pipes 28,29 are connected to inlet'ports, 30, -3'l.that communicatewith annulargrooves 32, '33 formed in the housing in encircling relationto the'liners I9, 20. At least one hole 34 is bored through the untaperedportion. ofeach liner in a manner to permitthe passage'of oil from thegrooves 32,

outlet pipe 3'! prober remain free of'bubbles and substantiallyincompressible, every effort should be made to eliminate any surfaceirregularities in the various y, Cap screws 25..

Disposed inencircling relar rings 21, but any desired l9, 20,Communicatadjustable toregu- Y tural rnerr'fber's of the ship'foroes'wiil-no'ttend to cause damage or undeparts which would create aturbulent condition during rotatmnnfthe shaft.

Connected io'mitably located in the housing l2 are gages 45-50 forindicating the hydraulic pressure at various points in the system. Sinceoil from both fore and aft between the piston EM and liners I9, 20, andtends to find its way past the sealing rings 21, I provide outletopenings 51, 52 ateach end of the housing beyond the outermost sealingrings 21 so that any excess oil may be drawn off.

The means for supporting the housing 12 will necessarily be designed tosuit the application, and in marine installations will vary from ship toship. In any case, however, the housing should :be seemed very rigidlyto supporting structure disposed-in a planelintersecting thelongitudinai vaxis of the shaft, or symmetrically about such a plane,votherwise. axial shaft movementswili tend to force the housing out ofits sa sa 39-44 the space 36 is forced drical surfaces proper parallelrelation-tome shaft. in the exampleshown, the housing 4.2 is veryrigidly secured, as :by bolts between spaced parallel beams 54 --andsupporting members 55 which are disposed longitudinally of the ship. t

variable; thrustsmust find their reaction either in the inertia of thepropelling system or in the-ship hull itself. theviscousgdamper reduoesthe motion'of itliejpropelling system, it reducesthe inertia.reaction'andthe main reaction must come from the huli'itself. Thisreaction is in the support of the viscous damper cylinder which must beattachedto the hull such .a position that no objectionable resonancesarise because of the introductionof the additional structure, This meansthat the viscous damper must be mounted as rigidly and as directly aspossible on strong longitudinal member-sci the ships hull.

Cantilever effects and the transmission of reaction through bendingstructures should be avoided. I The more directly the variable forcesact on compression members theless the possibilityoof ship vibrationtnoublesr Enough clearance, inch: perhaps, is provided in'the chamber 15at each end of the piston H to permit axial movement of thefshaftrelative to thehousing l2. The oil, confined in either end of thechamber l5 may gradually flow through the restricted space between" thepiston II and the liners i9, 20 so that the substantially steady axialthrust developed by t e propeller is transmitted to the usual thrustbearing at the forward end of, the shaft. jnnv'irapid highfrequency axialmovement ofthe shaft ID will be resisted'by the oilconfined betweenthe ends of the piston Handthe housing 12, since:the'joilis substantially incompressible and its flow between oppositeends of the chamber 1-5 is restricted by the relativelysmall clearancebetween the piston i l and: liners 119, 20, thus, any; objectionablehigh-frequency axiai forces in the shaft are taken by he housing l 2 andby the'longi'tudinal strucin a zone where such sirable vibration in theship.

Various changes may be made inthe form of invention herein shown anddescribed without dcpartingufrom the spirit not the invention or thescope of the following claims.

"Theinvention described herein may be manufacturedandnscdbym for theGovernment of the States of America :for governmental purposes withoutthe payment of any royalties thereon or therefor? lclaim: 1. Incombination with 'a'rotatable propeller shaft subject to high frequencyaxial movements, a piston fixed to the shaft and in coaxial alignmenttherewith, a cylinder surrounding the piston and of a length to permitreciprocation of the piston longitudinally of the cylinder, annularbearing means disposed within the cylinder intermediate the ends thereofand forming oil chambers in the opposite end portions of the cylinder,said bearing means including inside cylinof uniform internal diameterproviding a slight clearance about the piston inwardly of its ends andinside tapering surfaces providing increasing clearance toward the endsof the piston, means for introducing oil into the cylinder, and meansfor rigidly securing the cylinder against rotation and axial movement,

2. In combination with a rotatable propeller shaft subject to highfrequency axial movements,

ing the piston and of a length to permit reciprocation of the pistonlongitudinally of the cylinder, spaced annular liners disposed withinthe cylinder intermediate the ends thereof and forming oil chambers onein each end portion of the cylinder and one intermediate said endportions, said liners providing a slight clearance around the pistonpermitting restricted passage of oil between said oil chambers, meansfor maintaining oil under pressure in said chambers, and means forrigidly securing the cylinder againstrotation and axial movement.

3. In combination with a rotatable propeller shaft subject to highfrequency axial movements, a piston fixed on the shaft, a cylindersurrounding the piston and of a length to permit reciprocation of thepiston longitudinally of the cylinder, spaced annular liners disposedwithin the cylinder intermediate the ends thereof and forming chambersone in each end portion of the cylinder and one intermediate said endportions, saidliners providing a slight clearance around the pistonpermitting restricted passage of oil between said oil chambers, saidcylinder prov-idedwith annular grooves encircling the liners, means forintroducing oil into said grooves, said liners provided with oilchannels communicating with the oil chamber intermediate saidendportions, and with .oil ducts between said grooves and channels, saidcylinder provided with an oil outlet, and means for rigidly securing thecylinder against rotation and axial movement.

4. In combination with a rotatable propeller shaft subject tohigh-frequency axial movements, a piston fixed to the shaft andin-coaxialalignment therewith, a cylinder surrounding the pissaid linersincluding inner portions of uniform internal diameter providing av-smallclearance about the piston, and outer tapering portions of increasingintemaldiameter, means for introducing oil into the cylinder, and meansfor rig-idly securing the cylinder against rotation and axial movements.FRANK M. LEWIS.

